diff options
Diffstat (limited to 'curve25519-mul.c')
| -rw-r--r-- | curve25519-mul.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/curve25519-mul.c b/curve25519-mul.c index adb20cbc..f5127d77 100644 --- a/curve25519-mul.c +++ b/curve25519-mul.c @@ -72,7 +72,11 @@ curve25519_mul (uint8_t *q, const uint8_t *n, const uint8_t *p) itch = ecc->p.size * 12; scratch = gmp_alloc_limbs (itch); + /* Note that 255 % GMP_NUMB_BITS == 0 isn't supported, so x1 always + holds at least 256 bits. */ mpn_set_base256_le (x1, ecc->p.size, p, CURVE25519_SIZE); + /* Clear bit 255, as required by RFC 7748. */ + x1[255/GMP_NUMB_BITS] &= ~((mp_limb_t) 1 << (255 % GMP_NUMB_BITS)); /* Initialize, x2 = x1, z2 = 1 */ mpn_copyi (x2, x1, ecc->p.size); |